America’s war against terrorism marched forward on two fronts yesterday – as the United States unleashed a new round of punishing airstrikes in Afghanistan and jacked up security measures on the home turf.

“We’re going to be ongoing and relentless as we tighten the net of justice,” President Bush said. “This will be a long war.”

A holy-war declaration from the Taliban, warnings from Washington about the threat of fresh attacks, and an alarming anthrax outbreak in Florida provided a nerve-fraying backdrop to the bombs-and-missiles onslaught overseas.

“Strikes are continuing as we speak,” Air Force Gen. Richard Myers, chairman of the Joint Chiefs of Staff, said as the second bombardment began nearly 24 hours after an initial assault against 31 targets.

Blasts shook strategic installations in the capital Kabul, the Taliban stronghold Kandahar and the northern cities Mazar-e-Sharif and Kunduz while anti-aircraft fire ripped across the sky.

“The explosions were much more massive than last night,” one witness said after watching a hilltop transmitter get pounded. “I could see flames and debris rising from the foot of TV Mountain.”

The barrage – which began 26 days after the Sept. 11 atrocity at the World Trade Center and Pentagon – followed the Taliban’s refusal to hand over terror mastermind Osama bin Laden.

Five long-range bombers and 10 strike planes took part in yesterday’s assault, and two Navy ships and a submarine launched 15 Tomahawks.

The Pentagon described the first salvos as a partial success, but officials warned there was no “silver bullet” and the battle against terror will be waged on multiple fronts and could last years.

“It is very unlikely that the airstrikes will rock the Taliban back on their heels,” Defense Secretary Donald Rumsfeld said.

Washington, meanwhile, suggested in a letter to the United Nations that the offensive could extend to other countries.

“The United States reservesthe right to defend itself wherever it is necessary,” White House spokesman Ari Fleischer said, stressing that bin Laden isn’t the only target.

As the U.S. delivered its one-two punch, the Taliban dismissed the strikes as a failure.

At the same time, the regime that has ruled Afghanistan with an iron fist and harbored the world’s No. 1 fugitive since 1996 claimed unverified civilian casualties.

Its cabinet also approved a holy war previously voted on by clerics.

“The verdict of clerics is enforceable,” Information Minister Qudrutallah Jamal said. “They issued an edict for jihad, and our people are enforcing it.”

Bracing for revenge attacks, the Justice Department put federal law enforcement on its highest state of alert, Vice President Dick Cheney holed up at a secure location, and the Coast Guard mobilized its largest force since World War II.

The president addressed the public anxiety as he attended the swearing in of former Pennsylvania Gov. Tom Ridge as the director of the new Office of Homeland Security.

“I know that many Americans at this time have real fears,” Bush said. “We’ve learned that America is not immune from attack. We’ve seen that evil is real.”

There were growing fears that reality had come to bear in Boca Raton, Fla., where anthrax was found in the employees and offices of a supermarket-tabloid chain.

Authorities said a photo editor died of the rare disease, while a mailroom worker had been exposed to the deadly spores. A third worker was also said to have the germ.

The headquarters of American Media – which publishes the National Enquirer and The Sun – was sealed off, and staffers lined up at a clinic for testing and antibiotics.

The FBI took over the case, but said it was unknown if terrorism or an accident was the culprit.

“We regard this as an investigation that could become a clear criminal investigation,” Attorney General John Ashcroft said.